Lubricating-Fluid Infusion Apparatus

ABSTRACT

Infusion apparatus for dispensing lubricating fluid into a dynamic-pressure bearing device. Apparatus is made up of: a lubricating-fluid tank whose interior is filled partway with lubricating fluid; a vacuum chamber for placing the bearing device under a reduced-pressure environment; a nozzle for streaming the lubricating fluid into the bearing device; and a vacuum-evacuation system for evacuating and repressurizing the interior of the lubricating-fluid tank and of the vacuum chamber. Air dissolved into the lubricating fluid is eliminated by pumping-down the hollow, fluid-absent portion of the lubricating-fluid tank. Then repressurizing the hollow portion enables pressure to be applied to the lubricating fluid to force it out through the nozzle tip. The vacuum chamber interior may be pumped down to the optimum pressure for charging the bearing device with the lubricating fluid.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to lubricating-fluid infusion apparatusesfor dispensing lubricating fluid into dynamic-pressure bearing devicesemployed in signal record/playback devices such as hard-disk drives.

2. Description of the Related Art

(1) Dynamic-Pressure Bearing Device Structures

A variety of fluid dynamic-pressure bearings have to date been employedin spindle motors used in signal record/playback devices such ashard-disk drives. Fluid dynamic-pressure bearings provide journalsupport by producing fluid pressure in a lubricant, such as alubricating fluid, interposed in between a shaft and sleeve.

Single examples of spindle motors that employ a dynamic-pressure bearingof this sort are illustrated in FIGS. 10A and 10B.

The spindle motor in FIG. 10A is fit out with a dynamic-pressure bearingdevice 50, in which a lubricating-fluid taper seal section 53 is formed,in a single location only. The motor's shaft 51 is inserted into asleeve 52, wherein radial dynamic-pressure bearings 55, 55 supportradially directed load on the motor. Mounted on the shaft 51 at its tipis a thrust plate 56 where thrust bearings 58, 58 that bear axiallydirected load on the motor are formed. The bottom portion of the sleeve52 is closed off by a thrust bushing 57, wherein the bearing gapextending from the lubricating-fluid boundary surface in the taper sealsection 53 to the shaft tip is filled with the lubricating fluid,without any places in which the fluid is interrupted. The open portionof the bearing device, where the bearing gap meets the external air, isin the upper end only, and is where the taper seal section 53 is formed.

A bearing-device structure of this sort is highly reliable in that thesurface area of contact between the lubricating fluid and the externalair is small, and thus neither the mixing of air bubbles into, nor thegasification of, the lubricating fluid is liable to occur. Nonetheless,in order to inject lubricating fluid into the bearing device, air mustbe discharged ahead of time from the bearing gap, making equipment forthat purpose necessary.

The spindle motor in FIG. 10B is fit out with a dynamic-pressure bearingdevice 5′, in which the open portions of the bearing gap are in twolocations, above and below, which puts the taper seal sections 53, 53 inthe two locations above and below. Although evaporation of thelubricating fluid in a bearing-device structure of this type proves tobe fairly rapid, an advantage to the structure is that the centralstationary shaft can be employed, for example, as a support column forsupporting a hard-disk housing.

As far as the injection of lubricating fluid into the bearing device isconcerned, if for example lubricating fluid is poured into the taperseal section in the upper end, it spreads along by capillary action,heading downward through the successive gap sections, and the air isdischarged through the lower end. But the complex bearing-gapconformation means that there will be slight inconsistencies in the gapsections that give rise to differences in how the lubricating fluidspreads, leading to unequal permeation. Consequently, with thisstructure as well, it is necessary to discharge air ahead of time fromthe bearing gap.

In the final analysis, as long as a dynamic-pressure bearing device isnot especially structured for readily discharging air from its bearinggap, when the device is to be charged with lubricating fluid, it will benecessary to exhaust the bearing gap.

(2) Publicly Known Infusing Methods and Problems Therewith

Methods such as follows are examples of techniques for injectinglubricating fluid into the bearing gap, after air filling the gap hasbeen discharged, in dynamic-pressure bearing devices like device 50 or5′ discussed above.

(2-1) First Method

One is a method in which the bearing device and a container filled withlubricating fluid are put into a vacuum chamber, and with the chamber inan evacuated state, the open portion of the bearing gap is eitherimmersed in lubricating fluid or is submerged within lubricating fluid,after which air is introduced into the vacuum chamber to repressurizeit. The air pressure applied in repressurization forces the lubricatingfluid soundly into the full depth of the bearing gap.

Although this method may be realized with relatively simple facilities,the lubricating fluid sticks to the outside of the bearing device.Particularly in implementations in which the bearing device isincorporated into a hard disk drive, lubricating fluid having adhered tothe outside of the bearing device becomes a cause of fluid contaminatingthe disk(s). The adhered lubricating fluid therefore must be carefullywiped off, which makes necessary a manufacturing process step thatsignificantly impairs productivity. In implementations in which ascrew-hole into which a disk clamp is fastened is provided in the headof the shaft, the lubricating fluid permeates the screw-hole and thethread groove. Removing lubricating fluid that has permeated a narrowarea of this sort in the bearing device is extremely difficult.

(2-2) Second Method

An alternative technique is a method in which the bearing device is setinside a vacuum chamber, and with the chamber in an evacuated state acylindrical capillary tube such as a fine syringe needle is used totrickle lubricating fluid into the open portion, or the taper sealsection, of the bearing device, following which the chamber isrepressurized.

Employing this method might lead to the expectation that the processstep for wiping away lubricating fluid that has stuck to the outer sideof the bearing device could be omitted, but in actuality the method doesnot necessarily work well. This is because when the lubricating fluid issquirted from the needle tip, frequently the fluid froths at the tip andthe froth bursts, splattering on and contaminating the outside of thebearing device.

It might then seem that a way to get rid of the frothing would bebeforehand to sufficiently clear the lubricating fluid of air that hasdissolved into it. In practice, however, frothing occurs even if thelubricating fluid undergoes a degassing process, such that contaminationof the bearing device exterior is eliminated only with difficulty.

BRIEF SUMMARY OF THE INVENTION

A manufacturing apparatus of the invention that is the subject of thepresent application, utilized to charge a fluid dynamic-pressure bearingdevice with lubricating fluid, is made up of: a lubricating-fluid tankwhose interior is filled partway with lubricating fluid; a vacuumchamber for placing a dynamic-pressure bearing device under areduced-pressure environment; a nozzle for streaming the lubricatingfluid into the bearing device; and a vacuum-evacuation system forevacuating and repressurizing the interior of the lubricating-fluid tankand the interior of the vacuum chamber.

In this infusion apparatus, the pressure of the hollow, fluid-absentportion of the lubricating-fluid tank interior is reduced to eliminateair dissolved into the lubricating fluid. In turn, the hollow portion ispressure-elevated to apply pressure to the lubricating fluid and forceit out the nozzle tip. What this means is that both the function of adegassing vessel for carrying out a deaerating process on thelubricating fluid, and of a pressurizing chamber for developing pressurein the lubricating fluid to force it out are realized by means of asingle vacuum chamber. Moreover, because the internal pressure of thevacuum chamber in which fluid infusion is carried out can be controlledat will, frothing of the lubricating fluid when it is being dispensedcan be held in check.

An infusion apparatus of the present invention in another aspect enablesthe trickle-feeding of lubricating fluid inside the lubricating-fluidtank. The shock on and splashes formed in the lubricating fluid whenbeing trickled promote the removal of gas from the lubricating fluid,therefore making possible efficient minimizing of the concentration ofdissolved gas present in the lubricating fluid.

In another inventive aspect the infusion apparatus is equipped with astirring mechanism within the lubricating-fluid tank to enable efficientminimizing of the concentration of dissolved gas present in thelubricating fluid.

Another feature of an infusion apparatus of the present invention isthat its valve mechanism for controlling fluid dispensation has only twomodes, shutoff and open, and the switching between the two modes israpid. Inasmuch as the valve mechanism has only two modes, controllingit is rudimentary; thus the fluid delivery quantity may be controlledsimply by the length of time that the valve is open.

In this infusion apparatus, the valve shutoff is positioned adjacent thebasal portion of the nozzle, such that the amount of room from thelocation of the shutoff to the nozzle tip is extremely small. Therefore,in the interval from the valve shutoff to where the nozzle tip starts,sites where air bubbles would stay are essentially nonexistent. If thereare places where air bubbles form from the shutoff to the tip, when thevacuum chamber is repeatedly pumped down and repressurized, it canhappen that spurting of lubricating fluid remaining behind in the nozzlesection occurs, contaminating the infusion apparatus and thedynamic-pressure bearing device. However, utilizing the valve mechanismaccording to the aspect of the present invention just described enablessuch counterproductive nuisances to be reduced.

From the following detailed description in conjunction with theaccompanying drawings, the foregoing and other objects, features,aspects and advantages of the present invention will become readilyapparent to those skilled in the art.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view of a lubricating-fluid infusion apparatusinvolving the present invention;

FIG. 2 is schematic views of an dispensing device and a fluid tank;

FIG. 3 is magnified views of key portions of the dispensing device;

FIG. 4 is a diagram for explaining how the lubricating-fluid infusionapparatus operates;

FIG. 5 is an enlarged view of the seal section of a dynamic-pressurebearing device;

FIG. 6 is a second view of a dynamic-pressure bearing device sealsection;

FIG. 7 is a diagram for explaining a procedure to check for airencroachment;

FIG. 8 is a diagram for explaining a lubricating-fluid degassingprocedure;

FIG. 9 is a diagram for explaining a procedure to trickle-feedlubricating fluid into the fluid tank; and

FIG. 10 is views of spindle motors fit out with fluid dynamic-pressurebearings.

DETAILED DESCRIPTION OF THE INVENTION

(1) Lubricating-Fluid Infusion Apparatus

(1-1) Device Overall

Reference is made to FIG. 1, which illustrates a lubricating-fluidinfusion apparatus 1 for implementing a lubricating-fluid infusionmethod involving the present invention. The lubricating-fluid infusionapparatus 1 is made up of a vacuum chamber 2, an dispenser 3, alubricating fluid tank 4, and, for pumping down the interior of thesecomponents, a vacuum pumping device and a gas-introduction mechanism R,as well as their connecting supply lines.

In this implementation, a general rotary pump P is employed as thevacuum pumping device. The gas-introduction mechanism R, comprising aflow control valve W, and a filter F for preventing dust from invadingthe mechanism, introduces ambient air into the supply lines. To furtherensure that invasion of dust is prevented, the flow control valve Wadjusted to make it so that the air inflow speed does not growexcessively large. Reference marks G1 and G2 indicate Penning gauges,which enable the internal pressure of the vacuum chamber 2 and fluidtank 4 to be monitored.

The dispenser 3 is made up of a valve mechanism 30 (shown in FIG. 3) anda cylindrical capillary tube 32 mounted in the tip of the valvemechanism. The dispenser 3 is connected to the bottom portion of thefluid tank 4 through a feed duct 42. A dynamic-pressure bearing device 5is set inside the vacuum chamber 2, and is infused with lubricatingfluid supplied through the tip of the capillary tube 32.

The vacuum chamber 2 is of glass manufacture in a lidded cylindricalform that is open-ended along the underside; thus the status within thechamber may be observed from without. As depicted in FIG. 1, theopen-ended portion of the chamber along its underside is closed off by apedestal 21. This occlusion is maintained airtight by means of anot-illustrated O-ring made of rubber. The vacuum chamber 2 is connectedto the rotary pump P and the gas-introduction mechanism R viaventilation valves V and W.

FIG. 2 illustrates the fluid tank 4 and the dispenser 3. As depicted inFIG. 2A, an empty space 45 is left in the upper portion of the reservoir4, and by pumping down this space, the concentration of gas dissolved inthe lubricating fluid can be lowered. Relevant to that operation is aconduit 42 b connected to this region of the reservoir 4, through whichthe pressure of the empty space 45 is reduced/elevated. Duringpump-down, a stirring mechanism is operated to promote the reducing ofthe concentration of gas dissolved into the lubricating fluid. Thestirring mechanism is made up of a rod 44 furnished with a magnet, and astirrer 43 likewise furnished with a magnet, wherein rotating the rod 44rotates the stirrer 43 in the interior of the fluid tank 4. The fluidtank 4 interior is joined to the dispenser 3 via the feed duct 42, andin turn is joined to the exterior through the capillary tube 32 mountedin the tip of the dispenser 3.

In order to dispense lubricating fluid into the dynamic-pressure bearingdevice, a sufficiently large, stabilized ejection pressure must beattendant on the lubricating fluid sent into the dispenser 3. Otherwise,the fluid-dispensing volume will vary with each dispensing operation,which is prohibitive of assuring uniform product quality, especially incases in which bearing devices are mass-produced.

For that purpose, in the FIG. 2A instance, ejection pressure is impartedto the lubricating fluid by introducing air at atmospheric pressure intothe empty space 45. Meanwhile, represented in FIG. 2B is a differentmethod, in which ejection pressure is imparted to lubricating fluidstored within a cylinder 46 by placing a plummet 48 onto a plunger 47fitted into the cylinder 46. An advantage to the FIG. 2B method is thatpressure may be imparted to the lubricating fluid without exposing it toair. However, because the lubricating fluid once having been fed intothe fluid tank 4 can no longer be degassed, the fluid must be adjustedahead of time to adequately reduce the concentration of gas dissolved inthe fluid. Which of these two methods to choose is best decided by thetechnician taking other factors into consideration.

It will be appreciated that the infusion process can also be carried outon a plurality of dynamic-pressure bearing devices placed within thevacuum chamber 2. By sequentially shifting into place and performing theinfusion process on the dynamic-pressure bearing devices, lubricatingfluid can be infused into a plurality of dynamic-pressure bearingdevices with only a one-time evacuation of the vacuum chamber. In orderto execute this procedure, however, within the vacuum chamber 2 a jigonto which plural bearing devices can be set is necessary, as isinstalling a mechanism that shifts the jig. A jig and a mechanism ofthis sort may be, to give one example, a jig onto which a number ofdynamic-pressure bearing devices can be set, arrayed circumferentially,and a rotating mechanism designed to rotate the jig so as tosequentially shift each bearing device in turn into place directlybeneath the cylindrical capillary tube.

(1-2) Valve Mechanism

As will be detailed later, in the lubricating-fluid infusion apparatus1, with the interior of the fluid tank 4 in a reduced-pressure state inorder to degas the lubricating fluid, the capillary tube 32 tip is in asituation in which it is exposed to atmospheric pressure. Under thosecircumstances, external air tries to enter in, heading toward the fluidtank 4. Conversely, when the infusion apparatus 1 dispenses lubricatingfluid, on the one hand the tip of the capillary tube 32 is under reducedpressure; on the other, the empty space 45 is put at atmosphericpressure, imparting dispensing pressure to the lubricating-fluid. Underthese circumstances, the lubricating fluid tries to flow out, headingtoward the exterior. In either case, the flow has to be stopped with thevalve mechanism. Consequently, what is sought in a valve mechanism forthe dispenser 3 is that the valve will not give rise to leaking not onlywhen the internal pressure is in a higher state, but also when theexternal pressure is. A valve mechanism 30 of the structure illustratedin FIG. 3 can be employed as such a valve.

The description now turns to FIG. 3, a sectional view illustrating keyfeatures of the dispenser 3. From the end portion of the cylindricalcapillary tube 32, mounted in the tip of the dispenser 3, fluid isdispensed into the dynamic-pressure bearing device. Joined to the fluidtank 4 via the feed duct 42 is an inlet 34 through which lubricatingfluid imparted with delivery pressure is supplied. In a supply hole 35formed in a valve base part 31, an occluding rod 33 is accommodated forbeing pressed back and forth by a drive mechanism 38. When the occludingrod 33 is pressed downward in the figure by the drive mechanism 38, itcloses off an occlusion hole 37, forming a shutoff (FIG. 3A).Conversely, when the rod is drawn upward in the figure, the occlusionhole 37 is cleared, permitting the passage of lubricating fluid (FIG.3B). The drive mechanism 38 can be a device having the lone capabilityof simply shifting the occluding rod 33 back and forth, and can beconstituted from, for example, a spring and an electromagnet. Theoccluding rod 33 can thus be driven at high speed merely by electricalon/off switching.

In a valve mechanism 30 configured in this way, the occlusionestablished by the occluding rod 33 and the occlusion hole 37 is locatedextremely close to the basal end of the capillary tube 32 (nozzle);moreover, forward of the shutoff, there is no surplus cavity in whichair bubbles and the like would get stuck. The lubricating-fluid flowpathin the dispenser 30 running forward of the occlusion is constitutedalmost exclusively by the cavity in the interior of the cylindricalcapillary tube 32.

(2) Infusion Procedure

(2-1) Infusion Process

Initially the vacuum chamber 2 is lifted up into its opened state asindicated in FIG. 4A, and the dynamic-pressure bearing device 5 is setin a predetermined position atop the pedestal 21. To heighten theaccuracy with which the bearing device is located into place, a specialjig or a precision-movable stage may be employed.

In this state, the inside of the vacuum chamber 2 is at atmosphericpressure whereas the empty space 45 in the fluid tank 4 is continuouslyevacuated, wherein the space is pumped down to a pressure of 10 Pa(first pressure). At the same time, by the magnet-equipped rod 44rotating, the stirrer 43 plunged into the fluid tank 4 interior rotates,thus stirring the lubricating fluid. Gastightness between the fluid tank4 and the vacuum chamber 2 is maintained by the dispenser 3. With thelubricating fluid being exposed to an atmosphere of 10 Pa in pressure,the evacuation and stirring are continued. Under such conditions, theconcentration of gas present dissolved within the lubricating fluid maybe deemed to be at a concentration about in equilibrium with that of theatmosphere of 10 Pa in pressure.

Next the vacuum chamber 2 is lowered to close off its open-ended sideagainst the pedestal 21, and the interior is pumped down. The dispenser3 and the fluid tank 4 are lowered together with the vacuum chamber 2,shifting to a low position. As a result, the tip of the capillary tube32 is positioned into the seal section 53 (FIG. 5) formed in the openportion of the bearing gap of the dynamic-pressure bearing device 5. Atthe same time, as a result of the fluid tank 4 having shifted downward,the change in relative position of the rod 44 brings its magnetic forceout of action, and thus the stirrer 43 stops rotating, halting thestirring action.

Then the evacuation level for the vacuum chamber 2 is adjusted(pressure-adjusting step) so that the internal pressure of the vacuumchamber 2 will go to a pressure (second pressure) somewhat higher thanthe first pressure.

After that, in order to impart delivery pressure to the lubricatingfluid, ambient air is introduced into the empty space 45, raising it toatmospheric pressure. Ambient air is advantageous as the most readilyavailable source for supplying constant pressure. Nevertheless, thespace 45 does not necessarily have to be brought to atmosphericpressure, but according to requirements may equally well be broughtbeneath atmospheric or above atmospheric pressure, freely selected usinga suitable device.

Next, the valve mechanism 30 is opened for a predetermined duration todeliver the proper quantity of lubricating fluid that thedynamic-pressure bearing device 5 is meant to retain. At that time,although the lubricating fluid in the fluid tank 4 interior will havebeen exposed to air at atmospheric pressure, because the stirring willhave been stopped, in particular the lubricating fluid being drawn outfrom the lower portion of the fluid tank 4 will have been in a state ofapproximate equilibrium with the first pressure.

The lubricating fluid being ejected flows out from the tip of thecapillary tube 32. At that point, lubricating fluid flowing out from thetip of the capillary tube 32 will not froth, because the internalpressure of the vacuum chamber 2 will have gone to 30 Pa (secondpressure), which is greater than the first pressure. Therefore, theprocess of wiping up lubricating fluid having splattered due to frothingand become stuck to the dynamic-pressure bearing device can be omitted.What is more, the elimination of loss due to frothing reduces dispensingvolume variation, making the dispensing volume more accurate.

It should be noted that in advance of the pressure-adjusting step, theinterior of the vacuum chamber 2 may if necessary be momentarily pumpeddown to a pressure (fifth pressure) lower than the second pressure. Forexample, the chamber interior may be pumped down to the same 10-Pa levelas the first pressure. Doing so makes evacuation of the bearing evenmore thorough. Prior to fluid dispensing, however, the chamber must bepressurized to a pressure (second pressure) higher than the firstpressure to prevent the fluid from frothing.

(2-2) Status of Seal Section

FIG. 5 represents an enlarged view of the vicinity of the seal section53 of the dynamic-pressure bearing device 5 right after having beeninfused with fluid.

The seal 53 is formed in the open end of the bearing gap—marked withreference numeral 54 in the figure—in between the shaft 51 and thesleeve 52. The tip of the cylindrical capillary tube 32 is drawn nearthe seal 53, to just short of touching its wall surfaces, in which statethe lubricating fluid is dispensed. The shaft 51 constitutes abearing-device rotary component, and the sleeve 52 constitutes abearing-device stationary component. With the seal section 53 beingformed in the open portion of the bearing gap, it surrounds the rotarycomponent.

Lubricating fluid having been dispensed spreads around the entire theseal section due to its affinity for the seal-section wall surfaces, butdoes not reach the depths of the bearing gap 54. At this stage thelubricating fluid—marked with reference numeral 6 in FIG. 5—need notfill the seal section in its entirety, but must occupy the entirecircuit of seal area of the gap. Moreover, by the bearing-deviceenvirons having been pumped down to 30 Pa beforehand, the bearing gapwill have been pumped down to a pressure near that, and thus thelubricating fluid will be in a state in which due to its affinity forthe wall surfaces it will readily enter into the depths of the bearinggap. The right-hand side of FIG. 5 schematically represents theimmediate post-dispensing state of the fluid. Immediatelypost-dispensing the lubricating fluid 6 pools in the open portion of thebearing device, but by its affinity for the wall surfaces the fluidtransitions at once into the state sketched on the left-hand side of thefigure. In the figure left-hand side, the lubricating fluid has in partcrept into the depths of the bearing gap 54, lowering the liquid surfaceof the lubricating fluid in the seal section 53 by that extent.

Depending on the configuration of the seal section 53, and on thequantity of lubricating fluid that the bearing is meant to hold, in somecases the requisite amount of lubricating fluid cannot be dispensed in aone-time operation. In such cases, the fluid dispensing job may bedivided into two or more cycles. The second and subsequentfluid-dispensing operations then can be carried out by estimating thetime, following the first-cycle fluid-dispensing job, for thelubricating fluid to spread around the entire seal section 53 and itsliquid surface to drop sufficiently.

After the fluid dispensing operation is finished, the vacuum chamber 2interior is repressurized (third pressure). The repressurizationdevelops a pressure differential between the lubricating fluid 6interior/exterior, forcing the lubricating fluid 6 into the depths ofthe bearing gap 54 and completing the lubricating-fluid dispensing job.Although it is easiest to repressurize back to atmospheric pressure,repressurization to a pressure lower than atmospheric will not impedethe dispensing process, as long as the pressure is sufficient to forcethe lubricating fluid all the way into the bearing gap. In addition, thevacuum chamber 2 may again be evacuated and the fluid dispensing processcarried out again, once lubricating fluid has been forced into the gapand sufficient space in the seal section 53 has been secured.

Reference is now made to FIG. 6, which, like FIG. 5, is an enlarged viewof a bearing-device seal section, in this case in a dynamic-pressurebearing device 5′ in which the upper-end face of the sleeve has a slope60. A fluid-repellent film is formed on the slope and shaft surfaces. Inimplementations in which the dynamic-pressure bearing device isstructured in this way, the dispensed lubricating fluid fills over theslope (right half of the figure), and by capillary action subsequentlypermeates its way into the bearing gap (left half of the figure).Benefits of having the slope 60 are not only that a large volume oflubricating fluid may be dispensed at once, but also that lubricatingfluid does not get left behind on the upper-end face of the sleeve.

(2-3) Encroached Air Check

The dynamic-pressure bearing device 5 on which the dispensing procedurehas been finished is then run through a procedure to check for thepresence of air encroachment. Although the reliability of thebearing-device infusion method of present invention is extraordinarilyhigh, foul dispensings can arise nevertheless. Thus, inspection forexcluding such rejects is carried out.

FIG. 7 is a diagram for explaining this procedure. Thedispensing-processed bearing device 5 is put under atmospheric pressure.As far as the pressure environment for this procedure is concerned, aslong as the pressure is higher than a later-described fourth pressure,inspection is in principle possible, but atmospheric pressure, beingquite readily realized, is advantageous.

The dynamic-pressure bearing device 5 is set inside a vacuum case 91furnished with an evacuation mechanism, and anchored using a suitablejig. In that situation, the level of the lubricating fluid in a state inwhich atmospheric pressure has been applied is measured. The measurementis made using a laser displacement sensor 93, whose beam passes througha glass lid 92 on the vacuum case 91.

Next a vacuum pump P and a venting valve are operated to lower theinternal pressure of the vacuum case 91 to 1000 Pa, which is the fourthpressure. In this state, the fluid level is once again measured, and iscompared with the level before the pressure was reduced. If upon thissecond measurement the amount by which the level has risen exceeds apredetermined value, the device is excluded as a reject; if not, thedevice is rendered an acceptable item.

When the dynamic-pressure bearing device is shipped by airfreight, theaircraft will fly in the lower regions of the stratosphere, which atmaximum elevation is in the neighborhood of 14 km into the sky. At thatelevation the atmospheric pressure is on the order of 1 40 hPa, which isconsiderably larger than 1000 Pa (10 hPa). Consequently, if adynamic-pressure bearing device has passed the reduced-pressure test at1000 Pa, then even if the device is transported in a cargo bay that isnot pressurized in the least, the likelihood of fluid leakage occurringmay be deemed to be extremely small.

(2-4) Preprocess Lubricating-Fluid Degassing and Feeding into theInfusion Apparatus

The lubricating fluid that is fed into the lubricating-fluid infusionapparatus 1 is subjected to a special degassing process in advance,which shortens the time required for the degassing process within thefluid tank 4. In an infusion method of the present invention,lubricating fluid that is insufficiently degassed because the interiorof the fluid tank 4 is repeatedly exposed to the air may be deaeratedwith greater assurance in a separate vacuum chamber initially.

FIG. 8 illustrates the configuration of a degassing device utilized forsuch objectives. A vacuum case 9 is placed atop a magnetic-stirrer drivemechanism 8, and within a lubricating-fluid reservoir 7 inside the case9 lubricating fluid 6 is contained.

The vacuum case 9 interior is pumped down by a vacuum pump P to apressure lower than the first pressure. A good target is pumping down to10 Pa or less to keep on evacuating the case further. Long-term stirringin that state is continued, reducing dissolved gas until the level atwhich it is in equilibrium with this pressure ambient.

In addition to the advance degassing process, means may be devised so asto produce a deaerating effect when the lubricating fluid is fed intothe fluid tank 4. FIG. 9 represents a method of trickle feedinglubricating fluid into the fluid tank 4.

Specifically, the lubricating fluid is fed into a funnel 100, and via amicroflow valve 101 is trickled in drops into the fluid tank 4. Thefluid tank 4 interior is pumped down to 10 Pa or so. With the surfacearea per unit volume of the drops being large, degassing proceedsrapidly. And degassing is promoted further by the drops undergoing shockwhen they strike the inner surface of the fluid tank and the liquidsurface.

Not-illustrated heaters are attached to the vacuum case 9 and the fluidtank 4 utilized for the preprocess degassing. The lubricating fluid isdeaerated having been heated up by the heaters to 60 degrees. Degassingproceeds swiftly because in general the solubility of gasses in a liquiddrops as the temperature of the liquid rises.

The best mode, explained in the foregoing, for embodying the presentinvention is not limited by the content set forth herein. For example,as the dynamic-pressure bearing device into which lubricating fluid isdispensed, a shaft-rotating type has been depicted, but the effects ofthe present invention when applied to a shaft-stationary type ofdynamic-pressure bearing device do not alter. As a lubricating-fluidstirring mechanism, an example that employs a magnetic stirrer has beenillustrated, but rotating the stirrer by utilizing a terminal or otherdevice that introduces rotation into the vacuum chamber yields similareffects.

1. A lubricating-fluid infusion apparatus, comprising: lubricatingfluid; at least one vacuum-evacuation device; at least onegas-introduction source; a lubricating-fluid tank having an internalspace kept gastight against the exterior, said tank storing a volume ofsaid lubricating fluid smaller than the capacity of the internal space,and said vacuum-evacuation device and said gas-introduction source beingconnected to the tank hollow portion not filled with said lubricatingfluid; a supply line connected along one end to the portion of theinternal space filled with said lubricating fluid; a valve mechanismconnected to the other end of said supply line; a nozzle connected alongone end to said valve mechanism, the other end having a pointed tipconformation; and a vacuum chamber capable of accommodating at least thetip portion of said nozzle and at least a bearing-gap open portion of adynamic-pressure bearing device, said vacuum chamber being connected tosaid vacuum-evacuation device and said gas-introduction source.
 2. Alubricating-fluid infusion apparatus as set forth in claim 1, furthercomprising a lubricating-fluid introducing mechanism adapted fortrickle-feeding said lubricating fluid from outside to inside saidlubricating-fluid tank under conditions in which said tank hollowportion has been pumped down.
 3. A lubricating-fluid infusion apparatusas set forth in claim 1, wherein said lubricating-fluid tank is equippedwith a stirring mechanism for stirring said lubricating fluid, saidstirring mechanism being adapted for stirring said lubricating fluidinside said lubricating-fluid tank with the internal space within saidtank in a pumped-down state.
 4. A lubricating-fluid infusion apparatusas set forth in claim 2, wherein said lubricating-fluid tank is equippedwith a stirring mechanism for stirring said lubricating fluid, saidstirring mechanism being adapted for stirring said lubricating fluidinside said lubricating-fluid tank with the internal space within saidtank in a pumped-down state.
 5. A lubricating-fluid infusion apparatusas set forth in claim 1, wherein said valve mechanism is configured: tocreate a shutoff for shutting off, so as not to permit the lubricatingfluid to flow through, at least one place within a lubricating-fluidflowpath extending from one end of said supply line to the tip of saidnozzle; by forming and by undoing said shutoff, to produce at least twostates, an open state permitting said lubricating fluid to pass, and ashutoff state blocking off said lubricating fluid from passing; to allowsaid valve mechanism to be controlled so as to cut off fluid flow afterhaving been open for a predetermined period of time; and such that thetime required for the fluid-flow cutoff operation is so short comparedwith the time required for a single cycle of delivering said liquidthrough the flowpath as to be essentially negligible.
 6. Alubricating-fluid infusion apparatus as set forth in claim 2, whereinsaid valve mechanism is configured: to create a shutoff for shuttingoff, so as not to permit the lubricating fluid to flow through, at leastone place within a lubricating-fluid flowpath extending from one end ofsaid supply line to the tip of said nozzle; by forming and by undoingsaid shutoff, to produce at least two states, an open state permittingsaid lubricating fluid to pass, and a shutoff state blocking off saidlubricating fluid from passing; to allow said valve mechanism to becontrolled so as to cut off fluid flow after having been open for apredetermined period of time; and such that the time required for thefluid-flow cutoff operation is so short compared with the time requiredfor a single cycle of delivering said liquid through the flowpath as tobe essentially negligible.
 7. A lubricating-fluid infusion apparatus asset forth in claim 3, wherein said valve mechanism is configured: tocreate a shutoff for shutting off, so as not to permit the lubricatingfluid to flow through, at least one place within a lubricating-fluidflowpath extending from one end of said supply line to the tip of saidnozzle; by forming and by undoing said shutoff, to produce at least twostates, an open state permitting said lubricating fluid to pass, and ashutoff state blocking off said lubricating fluid from passing; to allowsaid valve mechanism to be controlled so as to cut off fluid flow afterhaving been open for a predetermined period of time; and such that thetime required for the fluid-flow cutoff operation is so short comparedwith the time required for a single cycle of delivering said liquidthrough the flowpath as to be essentially negligible.
 8. Alubricating-fluid infusion apparatus as set forth in claim 4, whereinsaid valve mechanism is configured: to create a shutoff for shuttingoff, so as not to permit the lubricating fluid to flow through, at leastone place within a lubricating-fluid flowpath extending from one end ofsaid supply line to the tip of said nozzle; by forming and by undoingsaid shutoff, to produce at least two states, an open state permittingsaid lubricating fluid to pass, and a shutoff state blocking off saidlubricating fluid from passing; to allow said valve mechanism to becontrolled so as to cut off fluid flow after having been open for apredetermined period of time; and such that the time required for thefluid-flow cutoff operation is so short compared with the time requiredfor a single cycle of delivering said liquid through the flowpath as tobe essentially negligible.
 9. A lubricating-fluid infusion apparatus asset forth in claim 1, said valve mechanism comprising: a valve basepart; a supply hole formed extending in one direction in said valve basepart, and having a mouth at an end portion thereof along said onedirection; an occluding rod inserted in said supply hole allowing saidrod to shift in said one direction and in the direction opposite to saidone direction, with a clearance enabling said lubricating fluid to flowaxially through being secured between said rod and the bore surface ofsaid supply hole; a cap part fitted onto said valve base part andcapping the mouth of said supply hole, said cap part therein fixed tomaintain a gastight seal between the rim of said supply-hole mouth, anda surface of said cap part running in said opposite direction; anocclusion hole having a mouth in said cap-part surface running in saidopposite direction and formed in a position where, by the occluding-rodend portion in said one direction being displaced along said onedirection, the rim of said occlusion hole is closed tight by saidoccluding-rod end portion, constituting a shutoff; and an occluding-roddrive mechanism for driving said occluding rod axially back and forth,to produce an occlusion-hole shutoff mode by forcing out the end portionof said occluding rod along said one direction, toward said occlusionhole, and pressing the tip of said occluding-rod end portion against therim of said occlusion hole, and to produce an occlusion-hole open modeby driving said occluding-rod end portion in said opposite direction;wherein said nozzle is mounted protruding from a surface of said cappart running in said one direction, the basal-end side of said nozzlebeing anchored buried into said cap-part surface running in said onedirection, and the hollow in the interior of said nozzle beingconnected, in the nozzle base portion, to said occlusion hole.
 10. Alubricating-fluid infusion apparatus as set forth in claim 2, said valvemechanism comprising: a valve base part; a supply hole formed extendingin one direction in said valve base part, and having a mouth at an endportion thereof along said one direction; an occluding rod inserted insaid supply hole allowing said rod to shift in said one direction and inthe direction opposite to said one direction, with a clearance enablingsaid lubricating fluid to flow axially through being secured betweensaid rod and the bore surface of said supply hole; a cap part fittedonto said valve base part and capping the mouth of said supply hole,said cap part therein fixed to maintain a gastight seal between the rimof said supply-hole mouth, and a surface of said cap part running insaid opposite direction; an occlusion hole having a mouth in saidcap-part surface running in said opposite direction and formed in aposition where, by the occluding-rod end portion in said one directionbeing displaced along said one direction, the rim of said occlusion holeis closed tight by said occluding-rod end portion, constituting ashutoff; and an occluding-rod drive mechanism for driving said occludingrod axially back and forth, to produce an occlusion-hole shutoff mode byforcing out the end portion of said occluding rod along said onedirection, toward said occlusion hole, and pressing the tip of saidoccluding-rod end portion against the rim of said occlusion hole, and toproduce an occlusion-hole open mode by driving said occluding-rod endportion in said opposite direction; wherein said nozzle is mountedprotruding from a surface of said cap part running in said onedirection, the basal-end side of said nozzle being anchored buried intosaid cap-part surface running in said one direction, and the hollow inthe interior of said nozzle being connected, in the nozzle base portion,to said occlusion hole.
 11. A lubricating-fluid infusion apparatus asset forth in claim 3, said valve mechanism comprising: a valve basepart; a supply hole formed extending in one direction in said valve basepart, and having a mouth at an end portion thereof along said onedirection; an occluding rod inserted in said supply hole allowing saidrod to shift in said one direction and in the direction opposite to saidone direction, with a clearance enabling said lubricating fluid to flowaxially through being secured between said rod and the bore surface ofsaid supply hole; a cap part fitted onto said valve base part andcapping the mouth of said supply hole, said cap part therein fixed tomaintain a gastight seal between the rim of said supply-hole mouth, anda surface of said cap part running in said opposite direction; anocclusion hole having a mouth in said cap-part surface running in saidopposite direction and formed in a position where, by the occluding-rodend portion in said one direction being displaced along said onedirection, the rim of said occlusion hole is closed tight by saidoccluding-rod end portion, constituting a shutoff; and an occluding-roddrive mechanism for driving said occluding rod axially back and forth,to produce an occlusion-hole shutoff mode by forcing out the end portionof said occluding rod along said one direction, toward said occlusionhole, and pressing the tip of said occluding-rod end portion against therim of said occlusion hole, and to produce an occlusion-hole open modeby driving said occluding-rod end portion in said opposite direction;wherein said nozzle is mounted protruding from a surface of said cappart running in said one direction, the basal-end side of said nozzlebeing anchored buried into said cap-part surface running in said onedirection, and the hollow in the interior of said nozzle beingconnected, in the nozzle base portion, to said occlusion hole.
 12. Alubricating-fluid infusion apparatus as set forth in claim 4, said valvemechanism comprising: a valve base part; a supply hole formed extendingin one direction in said valve base part, and having a mouth at an endportion thereof along said one direction; an occluding rod inserted insaid supply hole allowing said rod to shift in said one direction and inthe direction opposite to said one direction, with a clearance enablingsaid lubricating fluid to flow axially through being secured betweensaid rod and the bore surface of said supply hole; a cap part fittedonto said valve base part and capping the mouth of said supply hole,said cap part therein fixed to maintain a gastight seal between the rimof said supply-hole mouth, and a surface of said cap part running insaid opposite direction; an occlusion hole having a mouth in saidcap-part surface running in said opposite direction and formed in aposition where, by the occluding-rod end portion in said one directionbeing displaced along said one direction, the rim of said occlusion holeis closed tight by said occluding-rod end portion, constituting ashutoff; and an occluding-rod drive mechanism for driving said occludingrod axially back and forth, to produce an occlusion-hole shutoff mode byforcing out the end portion of said occluding rod along said onedirection, toward said occlusion hole, and pressing the tip of saidoccluding-rod end portion against the rim of said occlusion hole, and toproduce an occlusion-hole open mode by driving said occluding-rod endportion in said opposite direction; wherein said nozzle is mountedprotruding from a surface of said cap part running in said onedirection, the basal-end side of said nozzle being anchored buried intosaid cap-part surface running in said one direction, and the hollow inthe interior of said nozzle being connected, in the nozzle base portion,to said occlusion hole.
 13. A lubricating-fluid infusion apparatus asset forth in claim 5, wherein the fluid capacity of said flowpath whereit extends from said shutoff to the tip of said nozzle is approximatelyequal to the fluid capacity of the interior of said nozzle.
 14. Alubricating-fluid infusion apparatus as set forth in claim 6, whereinthe fluid capacity of said flowpath where it extends from said shutoffto the tip of said nozzle is approximately equal to the fluid capacityof the interior of said nozzle.
 15. A lubricating-fluid infusionapparatus as set forth in claim 7, wherein the fluid capacity of saidflowpath where it extends from said shutoff to the tip of said nozzle isapproximately equal to the fluid capacity of the interior of saidnozzle.
 16. A lubricating-fluid infusion apparatus as set forth in claim8, wherein the fluid capacity of said flowpath where it extends fromsaid shutoff to the tip of said nozzle is approximately equal to thefluid capacity of the interior of said nozzle.
 17. A lubricating-fluidinfusion apparatus as set forth in claim 9, wherein the fluid capacityof said flowpath where it extends from said shutoff to the tip of saidnozzle is approximately equal to the fluid capacity of the interior ofsaid nozzle.
 18. A lubricating-fluid infusion apparatus as set forth inclaim 10, wherein the fluid capacity of said flowpath where it extendsfrom said shutoff to the tip of said nozzle is approximately equal tothe fluid capacity of the interior of said nozzle.
 19. Alubricating-fluid infusion apparatus as set forth in claim 11, whereinthe fluid capacity of said flowpath where it extends from said shutoffto the tip of said nozzle is approximately equal to the fluid capacityof the interior of said nozzle.
 20. A dispensing apparatus comprising: avalve base part; a supply hole formed extending in one direction in saidvalve base part, and having a mouth at an end portion thereof along saidone direction; an occluding rod accommodated in said supply holeallowing said rod to shift in said one direction and in the directionopposite to said one direction, with a clearance enabling dispensingliquid to flow through being secured between said rod and the boresurface of said supply hole; a cap part fitted onto said valve base partand capping the mouth of said supply hole, said cap part therein fixedto maintain a gastight seal between the rim of said supply-hole mouth,and said cap part; a nozzle mounted protruding from said cap part,heading along said one direction; an occlusion hole having a mouth in aregion of said cap-part facing said valve base part, said occlusion holebeing formed in a position where, by the occluding-rod end portion insaid one direction being displaced along said one direction, the rim ofsaid occlusion hole is closed tight by said occluding-rod end portion,constituting a shutoff, and said occlusion hole being connected to thebasal-end side of said nozzle; and an occluding-rod drive mechanism fordriving said occluding rod in said one direction and in the directionopposite to said one direction, to enable said rod to assume at leasttwo positions, in one of the at least two positions, to shut off theocclusion hole by pressing the end portion of said occluding rod alongsaid one direction against the rim of said occlusion hole, and in theother of the at least two positions to permit the dispensing liquid toflow through by parting the end portion of said occluding rod along saidone direction away from the rim of said occlusion hole.